Induction disc type relay

ABSTRACT

An induction disc type relay adapted to apply to an induction disc a rotational torque proportional to an input so that an operating output is produced at the expiration of a predetermined time dependent on the magnitude of the input after the application of the input. Included in the relay are two sets of shading coils and reluctance paths responsive to the same input signal for applying the rotation torque to the induction disc, whereby and desired time lag characteristic can be readily obtained.

United States Patent Watai et al. 1 June 27, 1972 54] INDUCTION DISCTYPE RELAY 2,094,986 10/1937 Joumeaux ..310/172 2,027,846 1/1936 Suits..310/172 [72] 32;; 3'3" 2,110,686 3/1938 Verrall ..310/172 p 2,110,3913/1938 Davis ..310/172 [73] Assignee: Hitachi, Ltd., Tokyo, .la an2,110,417 3/1938 Green ..310/172 [22] Filed: 1970 Primary Examiner-J. D.Miller [21] Appl. No.: 91,013 Assistant Examiner-R. SkudyAttorney-Craig, Antonelli & Hill [30] Foreign Application Priority Data[57] ABSTRACT Nov. 21, 1969 Japan..... ..44/92969 An induction d typerelay adapted to apply to an induction disc a rotational torqueproportional to an input so that an US. Cl "310/136 operating output isproduced at the expiration of a predetep 58] Field 0 Search 6 268 181mined time dependent on the magnitude of the input after the 6application of the input. Included in the relay are two sets of shadingcoils andreluctance paths responsive to the same input signal forapplying the rotation torque to the induction [56] Rderences Cited disc,whereby and desired time lag characteristic can be readi- UNITED STATESPATENTS y Obtained- Courtin ..310/172 4 Claim, 7 Drawing FiguresPATENTEDmzv I972 3.6 73.446

SHEET 10F 3 F/G. Z PRIOR ART F/G. 3 PRIOR ART INVENTORS M \T6 0 W QT K YR ITO BY (11 a,, HM, W A ATTORNEYS PATENTEDJUN2? I972 3, 6 73 ,445

- INYENTORS Mn'suo wm-m KoYn ITO BY Ch W,WHW1

ATTORNEYS PATENTEDJUNZY I972 SHEET 3 0F 3 EXC/TA 770/V AMPERE- TURNS /V/INVENTORS ATTORNEYS mnucnou nrsc TYPE RELAY BACKGROUND OF THE INVENTION1 Field of the, Invention The present invention relates to inductiondisc type relays.

2. Description of the Prior Art An induction disc type relay isgenerally used as time lag relay which requires a predetermined timebetween the application of an input thereto and the generation of itsoperating output.

In FIG. 1, there is shown the operating characteristic of a time lagovercurrent relay which is the most frequently used application of theinduction disc type relay as a time lag relay and in this figure theabscissa represents the input current (in terms of multiples of the setoperating value) and the ordinate represents the operating current (inseconds), while curves (A), (B) and (C) represent what are usuallytermed an operating time lag characteristics.

While there has been formed no clear definition of each of the curves(A), (B) and (C), the curve (A) is generally defined as an inverse anddefinite'time lag characteristic showing that the operating time becomesshorter as the input current increases, but the: operating time becomespractically constant with the input current exceeding about ten timesthe value of the set operating value, while the curve (C) is called as avery inverse time lag characteristic showing that the operating timebecomes rapidly shorter in inverse proportion to the input current. Onthe other hand, the curve (B) is called an inverse time lagcharacteristic which is almost intermediate between the characteristicof the curve (A) and that of the curve (C). Although not shown in FIG.1, a characteristic showing the operating time whose rate of change withthe input currentis more rapid than is the case with the characteristiccurve (C) is termed an extremely inverse time lag characteristic, whilea characteristic which comes practically between those of the curves (A)and (B) is called a moderate inverse time lag characteristic.

It is well known in the art that these time lag characteristics may besuitably selected according to the kinds of apparatus to whichovercurrent protection must be afforded, and fault conditions etc.

In order that the operating time lag characteristic may be changed tosuit any input current, it is necessary to vary the driving torqueprovided to an induction disc. For example, the characteristic (A) maybe obtained if it is so arranged that the driving torque will becomeconstant with a current value exceeding 10 times the operatingvaIue,-while the characteristic (C)' may be obtained if it is soarranged that the driving torque remains on the increase so far as theinput current is within the illustrated range; The induction disc typerelays which are now in practical use may be divided into two broadclasses according to the kinds of driving electromagnets used, that is,a transformer (split phase) type relay as shown in FIG. 2 and a shadingcoil type relay as shown in FIG. 3.

These two types ofrelays will now be briefly described. Firstly, thetransformer type relay shown in FIG. 2 includes a core 1 provided with amain pole 2 and magnetic poles 3 formed thereon, and a primary coil 4 towhich an input is applied and a secondary coil 5 are both wound on themain pole 2 with one end of the secondary coil 5 being wound on asaturable transformer 6. One end of another coil wound on the saturabletransformer 6 is connected to a magnetic pole coil 7 wound on themagnetic poles 3. Numeral 8 designates an induction disc rotatablydisposed in an air gap between the main pole 2 and the magnetic poles 3.

I With the construction described above, it is so arranged that themagnetic path of the primary coil 4 is readily saturable and at the sametime the magnetic pole coil 7 is excited by the secondary saturationcurrent of the saturable transformer 6 to saturate the driving torque onthe induction disc 8.

. Therefore, while the transformer type relay is well suited to obtainan inverse and definite time lag characteristicsuch as thecharacteristic (A), it has a drawback in practical use in that theconstruction is complicated compared to the shading coil type relay,that the operation of winding the primary coil 4 and the magnetic polecoil 7 is a diflicult undertaking and hence the working efliciency islow, and that the apparent power consumption in tenns of voIt-amperes ishigh.

On the other hand, as shown in FIG. 3, the driving electromagnet portionof the shading coil type relay includes a core 9 on which is wound anexciting coil 10 to which an input is applied, and the air gap portionsof the core 9 are formed into the shape of forks by means of a slot 11so that a shading coil 12 is wound on one of the respective forkedpoles. An induction disc 13 is also disposed in the air gap formed bythe core 9 so that the induction disc 13 rotates about a shaft 14 withinthe air gap.

Then, as an input is applied to the exciting coil 10 and the I disc 13is rotated by the shifting magnetic field, an operating output isproduced when the disc 13 rotates 'through a predetermined angle, thatis, an operating output is delivered at a specified time after theapplication of the input.

In this manner, the shading coil type relay performs the time lag actionthereof, and its advantages include a very simple construction which canbe completed by simply mounting the shading coils and hence good workingability and a low apparent power consumption (volt-ampere) as comparedwith the transformer type relay are obtained.

However, since the shading coil type relay has a relatively large airgap portion in the magnetic circuit thereof, it is difficult to obtain adefinite time lag characteristic, even if a core material is used whichexhibits an almost rectangular hysteresis characteristic, and so theshading coil type relay is suited for applications where it is desiredto obtain such an operating time characteristics as the characteristics(B) and (C).

The experiments conducted by the inventors have shown that a definitetime lag characteristic satisfactory for the most part could be obtainedif a 78 percent Permalloy (nickel content, 78 percent) having an almostrectangular hysteresis characteristic (i.e., the saturation density isconstant) were used as a core material, but Permalloy is very expensiveand has the drawback of increasing the cost of a relay incorporating it.

SUMMARY OF THE INVENTION The present invention aims-at eliminating thedeficiencies described above and therefore one object of the presentinvention is to provide an induction disc type relay of a shading coiltype which is capable of easily obtaining not only an inverse time lagcharacteristic, but also an inverse and definite time lagcharacteristic.

Another object of the present invention is to provide an induction disctype relay which is very simple in construction and low in powerconsumption (volt-ampere).

A further object of the present invention is to provide an inductiondisc type relay which is inexpensive and capable of achieving theexpected effects without using any special and expensive material as thecore material.

Those and other objects and features of the present invention will bereadily apparent from the following descriptions of the preferredembodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagram showing the timelag characteristic of a time lag overcurrent relay which is the mosttypical of the applications of induction disc type relays;

FIG. 2 is a schematic diagram showing the driving section of atransformer type relay;

FIG. 3 is a schematic diagram showing the driving section of a prior artinduction disc type relay;

FIG. 4 is a schematic diagram showing the principal part of anembodiment of the present invention;

FIG. 5 is a plan view schematically showing the induction disc used inthe device of FIG. 4;

FIG. 6 is a diagram for explaining the operation of the device of thepresent invention; and

FIG. 7 is a schematic diagram showing the principal part of anotherembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 illustratesdiagramatically the driving section of an induction disc type relayaccording to the present invention. In the figure, numeral designates anexciting coil wound on a core 16, 17 a rotary disc which rotates about ashaft 18 within air gaps, g, and 3 as shown in FIG. 5, thereby closingthe contacts which are not shown. The magnetic pole portions where themagnetic flux in the core 16 interlinks the disc 17 are divided intopairs of magnetic poles 19, 19 and 20, 20' and each of these poles 19,19 and 20, 20' is in turn forked so that shading coils 21, 21', 22 and22' are mounted at the respective positions of the forked poles. Theseshading coils 21, 21', 22 and 22 are positioned as shown in the figureso that torques produced at the respective shading coils tend to opposeeach other. Numeral 23 designates a restraining spring having one endconnected to the shaft 18 and the other end to some relay member so thatwhen the disc 17 rotates in the normal'direction of movement thereof,the spring 23 produces a definite restraining torque in the directionopposite to the direction of movement of the disc 17.

Although not shown in the figure, a permanent magnet (braking magnet) isseparately provided to retard the motion of the induction disc 17 so asto give a time lag as with those induction disc type relays which arenow in practical use.

With the construction described above, when an input is applied to theexciting coil 15, the magnetic flux produced in the magnetic poles 19,19' interlinks or passes through the disc 17 to rotate it clockwise,thereby producing an operating torque in the direction to close therelay contacts. On the other hand, the magnetic flux produced in themagnetic poles 20, 20 rotates the disc 17 counter-clockwise to produce arestraining torque in the direction to restraint the closing of thecontacts. As a result, the disc 17 will be driven by the differencebetween the torque produced by the poles 19, 19' and that by the poles20, 20'.

Now consider the construction of the magnetic circuit comprising-thecore 16 as the principal part thereof and the magnetic reluctance of themagnetic path between points A and B on the core including the pole airgaps. The air gap g, of the magnetic path including the poles 19, 19'may be selected to be smaller than the air gap g; of the magnetic pathincluding the'poles'20, 20' so that the reluctance of the former willremain smaller than that of the latter until the magnetic path betweenthe points A and B become saturated, while the cross-section of thepoles 19, 19' may be made smaller than that of the poles 20, 20' so thatthis portion will become saturated first.

With the magnetic paths arranged as described above, the relationshipsbetween the excitation ampere-turns of the exciting coil 15 and themagnetic flux in each of the magnetic poles are as shown in FIG. 6.

In FIG. y, qS, designates the magnetic flux passing 6, the poles l9, I9;45 the magnetic flux passing through the poles 20, 20'; T, and T,torques produced by the magnetic fluxes d), and respectively. Now, ifthe constants of the torques T, and T are K, and K respectively, thesetorques T, and T are given by the following equations:

T, K, 4), (clockwise) (1) T K da (counterclockwise) (2) Then, a torque Tfor driving the disc 17- is given by T T, T

If the restraining torque as produced by the restraining spring 23 is Tthen the composite torque Twhich is to be applied to the disc 17 isgiven by r"' 2"' o Thus, if the result is positive, the disc 17 will berotated to close the contacts.

Assuming now that the magnetic flux d), remains to be proportional tothe excitation ampere-turns of the coil 15 after it has reached thesaturation magnetic flux while the magnetic flux will not be saturated,but it remains to be proportional to the excitation ampere-turns of theexciting coil 15, then the following equations result:

Considering the constants put in the bracket in the second member on theright side of the equation (9), K, may be varied by means of thereluctance of the magnetic path including the poles 20, 20', i.e., theair gap g the cross-section of the magnetic poles etc., while K may bevaried by means of the shading coils 22, 22. In other words, theconstant K will be zero in the absence of the shading coils 22, 22'.

Then, if the value of the bracketed second member on the right side ofthe equation (9) is reduced to zero within the range of the inputcurrent shown in FIG. 1, the combined torque Tcan be made constantindependent of the excitation ampere-turns of the exciting coil 15,i.e., the input current and hence the operating time can necessarily bemade constant, thereby giving a definite time lag characteristic.

However, as will be seen from the equation (9) and FIG. 6, the value ofthe bracketed second member on the right side of the equation (9) cannot be reduced to zero, whereas if, for example, the constant K of therestraining torque T is changed to K, and the value of this constant K,is so chosen that the operating torque T, and a restraining torque T,increase at the same rate, the value of this bracketed member can bealmost reduced to zero so that the combined torque T can remain constantwith respect to the input after a certain point has been reached.

On the other hand, if it is so chosen that the ampere-turns required forthe magnetic flux d), to become equal to the saturation magnetic flux 41are obtained at a near point a of the curve (A) in FIG. 1, that is, witha current of about ten times the set operating value, the time lagcharacteristic of such a relay can take the form of an inverse anddefinite time lag v characteristic as shown by the curve (A) in FIG. 1.

Furthermore, if the constants K and K, are so chosen that therestraining torque T in the counter-clockwise direction becomes smaller,the combined torque T will increase as the excitation ampere-turns ofthe exciting coil 15 increase, so that the operating time becomesgradually shorter as the input increases to approach the characteristicsshown at (B) and (C) in FIG. 1, thereby giving an inverse time lagcharacteristic and a very inverse time lag characteristic.

It is now evident from the foregoing that according to the presentinvention a core adapted to be energized by an exciting coil is formedwith two pairs of magnetic poles for producing an operating torque and arestraining torque, respectively, so that any desired time lagcharacteristics ranging from an inverse and definite time lagcharacteristic to a very inverse time lag characteristic can be obtainedwith varying values of the restraining torque which may be accomplishedby changing the related constants by means of the air gaps and thecrosssection of the poles which produce the restraining torque.

Thus, one of the very important features of the present inventionresides in that an inverse and definite time lag characteristic whichhas been considered as hardly attainable with conventional relays,particularly the induction disc type relays, is now obtainable withextreme easiness according to the present invention.

While the magnetic poles for producing the operating torque and therestraining torque are formed on the same core in the embodiment shownin FIG. 4, another embodiment of the present invention in which suchmagnetic poles are formed on different cores will now be explained withreference to FIG. 7. In FIG, 7, numerals 23 and 24 designateelectromagnets for producing an operating torque and a restrainingtorque, respectively, and the electromagnet 23 comprises a core 27 whichis provided with magnetic poles 26, 26 with shading coils 25, 25' and onwhich is wound an exciting coil 28 to which an input is applied, wherebythe operating torque in the direction of an arrow 30 is produced on aninduction disc 29 rotatably disposed between the magnetic poles 26, 26.The electromagnet 24 similarly comprises a core 33 which is providedwith magnetic poles 32, 32.with shading coils 31, 31 and on which iswound an exciting coil 34 to which the same input as with theelectromagnet 23 is applied, so that a restraining torque in' thedirection of an arrow 35 which is opposite to the direction of theoperating torque produced by the electromagnet 23, is produced on thedisc 29 or some other disc which is mechanically coupled to the disc 29.Thus, the same effects as obtained with the embodiment of FIG. 4 can beachieved by suitablyselecting the value of the constant of theelectromagnet 24, such as by varying the air gap of core 33 with respectto core 27 of electromagnet 23.

As described hereinbefore, according to the present invention means areprovided to produce both an operating torque and a restraining torque,i.e., a rotational torque on an induction disc, whereby the means forapplying the restraining torque may be controlled to suitably select andregulate the restraining torque so as to obtain any desiredcharacteristics including not only an inverse time lag characteristicand a very inverse time lag characteristic, but also an inverseand'definite time lag characteristic.

Furthermore, since an inverse and definite time lag characteristic whichhas hitherto been obtainable only with transformer type relays can beobtained with induction disc type relays, such an inverse and definitetime lag characteristic is now attainable with relays which are low inthe apparent power consumption (volt-amperes), easy to manufacture andsuperior in economy. MOreover, any good time lag characteristic can beobtained with inexpensive relays, since such a good characteristic isobtainable without using specific and expensive alloys such asPerrnalloy but using inexpensive material such as silicon steel as acore material.

While the present invention has been described with reference to theparticular embodiments of the invention, it should be apparent to thoseskilled in the art that many other embodiments can be conceived withoutdeparting from the scope of the spirit of the present invention.

We claim:

1. In an induction disc type relay including an induction disc and meansfor applying a rotational torque to said disc, the improvement whereinsaid means for applying a rotational torque to said disc comprises:

first means, responsive to an input signal, for supplying a firstoperating torque to rotate said disc in a first direction; and

second means, responsive to said input signal to which said first meansis responsive, for supplying a second operating torque to rotate saiddisc in a direction opposite to said first direction, wherein said firstand second means each comprises a shading coil magnetic pole structurehaving differently spaced air aps mounted on the single core piece,where y, the resultant torque applied to rotate said disc results fromthe application of the same input signal to said first and second means,so that a desired inverse time lag characteristic can be accuratelyobtained.

2. An induction disc type relay according to claim 1, wherein said discis mounted on a shaft having a bias spring provided therefor to impart abias torque to said disc in one of said directions.

3. An induction disc type relay according to claim 2, including asingular input coil mounted on said core structure to which said inputsignal is applied. Y

4. In an induction disc type relay including an induction disc and meansfor applying a rotational torque to said disc, the improvement whereinsaid means for applying a rotational torque to said disc comprises:

first means, responsive to an input signal, for supplying a firstoperating torque to rotate said disc in a first direction; and

second means, responsive to said input signal to which said first meansis responsive, for supplying a second operating torque to rotate saiddisc in a direction opposite to said first direction,

wherein said first and second means each comprises a shading coilmagnetic pole structure having differently spaced air gaps mounted onseparate core pieces and including a pair of input coils mounted on saidpieces and having the inputs thereof each receiving said input signal sothat said input signal will be applied to each of said core pieces and,thereby, to said shading coil magnetic pole structure, whereby, theresultant torque applied to rotate said disc results from theapplication of the same input signal to said first and second means, sothat a desired inverse time lag characteristic can be accuratelyobtained.

1. In an induction disc type relay including an induction disc and meansfor applying a rotational torque to said disc, the improvement whereinsaid means for applying a rotational torque to said disc comprises:first means, responsive to an input signal, for supplying a firstoperating torque to rotate said disc in a first direction; and secondmeans, responsive to said input signal to which said first means isresponsive, for supplying a second operating torque to rotate said discin a direction opposite to said first direction, wherein said first andsecond means each comprises a shading coil magnetic pole structurehaving differently spaced air gaps mounted on the single core piece,whereby, the resultant torque applied to rotate said disc results fromthe application of the same input signal to said first and second means,so that a desired inverse time lag characteristic can be accuratelyobtained.
 2. An induction disc type relay according to claim 1, whereinsaid disc is mounted on a shaft having a bias spring provided thereforto impart a bias torque to said disc in one of said directions.
 3. Aninduction disc type relay according to claim 2, including a singularinput coil mounted on said core structure to which said input signal isapplied.
 4. In an induction disc type relay including an induction discand means for applying a rotational torque to said disc, the improvementwherein said means for applying a rotational torque to said disccomprises: first means, responsive to an input signal, for supplying afirst operating torque to rotate said disc in a first direction; andsecond means, responsive to said input signal to which said first meansis responsive, for supplying a second operating torque to rotate saiddisc in a direction opposite to said first direction, wherein said firstand second means each comprises a shading coil magnetic pole structurehaving differently spaced air gaps mounted on separate core pieces andincluding a pair of input coils mounted on said pieces and having theinputs thereof each receiving said input signal so that said inputsignal will be applied to each of said core pieces and, thereby, to saidshading coil magnetic pole structure, whereby, the resultant torqueapplied to rotate said disc results from the application of the sameinput signal to said first and second means, so that a desired inversetime lag characteristic can be accurately obtained.